Multiple Regulator setup?

I wanted to use Carnetix regulators to power my many USB ports for my build, but I can't do 5v on both outputs so what I planned was 19v/5v for my PC & the front USB ports & 12v/5v for my screen & the rear ports. I was bummed to see the 1900 didn't do 12v/5v but the 2140 was mentioned as it can do 12v/5v .... but since the 5v is only 3 amps, would it be optimal to stick with the single 1900 at 19v/12v, and add on a P5V for a 3rd output, using a couple more for the back, if needed? I'd want to provide 1 amp to the exposed ports (for charging devices) as any connected device would be using hidden 500mA USB ports.

I play around with 5 volt setups quite a bit, and you can definitely do better efficiency and higher output current at a lower price than the P5V.

To quote myself and save typing:

Selecting a Power Supply
In my original version of this article, I used the Carnetix PNX-P5V linear regulator. The article goes in-depth on the installing the PNX-P5V in the Sheeva Plug's case. I later realized the PNX-P5V was a terrible idea. Heres why:

In the simplest terms, a linear regulator works by taking in a high-voltage and "burning off volts" to reach the desired voltage. What does this look like for efficiency? Terrible. The average power consumption of the plug is 5 watts. That means 5 volts at 1 amp. To produce this from a 12 volt input we need to burn off 7 volts at 1 amp. This brings the total power consumption to 12 volts at 1 amp. 12 watts in, 5 watts out. 41.7% efficiency.

Switching regulators do significantly better. They are able to achieve efficiencies of over 90%, however they require more components and thus take up more space. I now use and recommend the Mean Well SD-50A-5 which can pump out 5 volts at 10 amps and has a wide input range of 9.2 volts to 18 volts. Perfect for a car. 50 watts is far more power than neccessary but I chose to use it as a power supply for many other devices as well. To cut down on cost and size I can also recommend the 15 watt SD-15A-5, which matches the AC adapter's output specs exactly or the 25 watt SD-25A-5 which gives you more room.

As a final note on power supplies, if you only intend to run the sheeva plug when the car is running, the PNX-5V is not a bad choice. Minus its terrible efficiency, it served me well for over a year. However, my Sheeva Plug runs off of my car battery 24/7 and in that situation, 43% efficiency just doesn't cut it.

On another note:
Outside of hard drives, USB devices rarely consume 500mA, unless of course they are charging. Keep that in mind when calculating power. Check each individual device's spec. USB hubs themselves average 100mA.

To stay within spec, USB hubs will generally limit themselves to 500mA on the source USB port. 500mA - 100mA = 400mA left for devices on that hub to share. So make sure in your setup, you use hubs that are capable of being "externally powered" and use their power input port to supply them with power.

I realize I went off in a few different directions here I was typing in a hurry, hopefully this post is at least partially useful to you. haha

Here's my plan in more detail:
I plan to have a hard drive array for USB Drives in my center console. Looking to do 4 ports. I'm unlikely to use all 4, but if friend wants to bring an external drive so they can access their library on a road trip or something, I'd be happy to accommodate. In the center console itself I plan to have 2 exposed data-connected USB ports. MAYBE 4, just to plan ahead. As needs arise I may want an internal hub for additional peripherals, as well (looking at 3 4-port hubs with data, so far. I know for a fact I will have the "front" USB port on my ZBOX run direct to the dash for plugging in a keyboard to troubleshoot. This port, I'm told, is the only one you can use to get into the BIOS as the others don't activate right away. That info may be incorrect but I see no harm in that.

For the back seat, I'll have a 4-port hub in the back of the center console, or possibly in the middle armrest (I'm taking out the seat belt and my car will only seat 4) for device charging. Each door will also sport a USB port for device charging and an internal USB port with audio adapters for multizone audio (headsets).

so, 12 for charging, I want 1A each, preferably. 4 for hard drives, will need 500mA each. And 8 connected ports, I'd like to do 500mA each, to be safe, at least for the one in the dash, I'm not sure on the watts used by the audio adapters I have in mind (logitech brand).

Between cell phones, mp3 players & tablets, it's isn't out of question to think that I might have all the ports in use during a road trip. The Mean Well SD-50A-5 sounds perfect for the charging ports. I may use that for all 12 charging ports... it's unlikely I'll ever have more than 10 amps being pulled on those ports.

What I meant to ask Paul though is do these stepdown converters regulate power? I notice that yours do, but it doesn't mention it for the ones I am eying. On the pages it says: With overload / over-current / over / low voltage protection, stable performance. So does that mean it does regulate power, because my thought was that these things step down voltage in the form of heat. So if unregulated power is going into it, doesn't that mean it will be spitting out unregulated 5V power?

Sorry if it seems like I am thread jacking, but I wanted to recommend this item to you Ryven, but I want to make sure its a safe solution and Paul may know. If my solution works, you can consolidate all your 5V needs to one regulator.

My setup uses 31+ USB ports between 2 computers, so I feel your pain. I am also designing toggle USB ports for the center consoles and powering them all would be easier if I can power them via one converter.

What I meant to ask Paul though is do these stepdown converters regulate power? I notice that yours do, but it doesn't mention it for the ones I am eying. On the pages it says: With overload / over-current / over / low voltage protection, stable performance. So does that mean it does regulate power, because my thought was that these things step down voltage in the form of heat. So if unregulated power is going into it, doesn't that mean it will be spitting out unregulated 5V power?

Sorry if it seems like I am thread jacking, but I wanted to recommend this item to you Ryven, but I want to make sure its a safe solution and Paul may know. If my solution works, you can consolidate all your 5V needs to one regulator.

My setup uses 31+ USB ports between 2 computers, so I feel your pain. I am also designing toggle USB ports for the center consoles and powering them all would be easier if I can power them via one converter.

He absolutely could use the current logic supplies too, I'm just reluctant to recommend a product that I've never used. He also definitely doesn't need more than 10 amps in his application.

Yes, those look like they are regulated judging by the fact that they say they are stable. Unfortunately, the links to real spec sheets don't actually work. I have doubts that there are many DC-DC 5 volt power supplies that aren't regulated though...

Earlier I tried finding the mp3car'er with (IMO) a great 5V multi-Amp supply (like about 10A at (IMHO) a great price) but I didn't find it.

As to DC converting supplies, they should all be (voltage) regulated - the question is how effectively and how fail-safe? But I assume linear is out of favor for at least heat & efficiency reasons, and (SMPS) dc-dc converters tend to be more stable or have greater protection (like shutdown if failed or an out-of-spec output voltage).
Plus that dc-dc converters can do up conversion. Or rather, they do not need a minimum of (say) 5V+3V = 8V for proper regulation - that's nice in a 12V car environment for digital applications.

OK, so what I'll do, is I will buy the one I linked to and do some testing. It says it has over voltage protection and what not. I will also ask them what the failure rate is, I don't want to get into something that I'll have to replace every couple of months and could damage my equipment.

Are you sure about that range? For auto use?
The 12V-in requires 10V upwards. IMO that isn't adequate for 12V mobile/auto use.
And not being reverse polarity protected... (though all it needs is a MOSFET, or relay & diode).

Are you sure about that range? For auto use?
The 12V-in requires 10V upwards. IMO that isn't adequate for 12V mobile/auto use.
And not being reverse polarity protected... (though all it needs is a MOSFET, or relay & diode).

Are you talking about the product im talking about? Well my truck puts out 11.5 when off, and 12V when on. Since the PC will control the converter, the PC will have shut everything off once it gets under 11V.

Explain the MOSFET and or relay setup please. How are you finding out info on this, I cant seem to find anything except whats on their site.

I suspect many envy you if you don't get dips below 11V when driving - even when charging at 14.4V etc. But if the PSUs/loads have sufficient hold up time, all is fine.
Cranking sags/dips are another issue...

Reverse polarity protection by using a diode and a relay - as used for car IGN relays (for ECUs etc) and often incorporated...
A MOSFET can be used for the same.

Those were all general (knowledge) recommendations - nothing off that site AFAIK.